London, Feb 15 (IANS): Children exposed to smoking at home have lower levels of an enzyme that helps them respond to asthma treatment, a study finds.

Passive smoking is known to worsen asthma symptoms in children and impair their response to inhaled steroid treatment, but how this effect occurs was not known till date.

Researchers at Imperial College London found that children with severe asthma with a parent who smokes at home have lower levels of the enzyme 'HDAC2' compared with those whose parents don’t smoke.

'HDAC2' is required for steroids to exert their beneficial anti-inflammatory effects in asthma.

“The mechanism we’ve identified makes children less sensitive to inhaled steroid treatment, so they suffer more symptoms and might have to take higher doses of steroids, which may lead to side effects,” said professor Peter Barnes from Imperial College London.

“These findings underline the importance of legislation aimed at protecting children from being exposed to cigarette smoke,” he added.

It is estimated that one out of every 12 children in India has asthma and the number is rising constantly with rise in pollution levels in cities.

Taking cross-section of the population, it is estimated that 3-10 percent suffer from asthma and allied problems.

Steroid treatments, usually taken using inhalers, are given to prevent asthma attacks, but for many patients, they aren’t completely effective.

“Children with asthma who are passively exposed to cigarette smoke have the same molecular abnormalities that lead to steroid resistance as adults who actively smoke,” said professor Barnes.

The mechanism would be a target for new treatments to help children with severe asthma, claimed the study published in the journal Chest.